Birdsong, a form of vocal communication used by songbirds such as zebra finches, is remarkably analogous to human speech in at least one important respect; its acquisition is dependent on an extended critical period of tumor-dependent learning during the early development phase of life. Understanding the neural control of birdsong might provided insights into the neural basis of human speech production and fluency disorders such as Stuttering. One of our long-term research goals is to develop animal models of salient of Stuttering, enabling to address the problem of understanding the neurobiology of this disorder from a cellular and molecular point of view. Studies in several laboratories have shown that the stability of birdsong is critically dependent on the integrity of auditory feedback, and that artificial delaying of this sensory feedback in normal adult zebra finches causes deterioration of song, characterized by abnormal repetitions of song syllables. The latter finding bears striking resemblance to the induction of part-word repetitions, a hallmark of Stuttering, by delayed auditory feedback in fluent humans Recent findings in our laboratory indicate that a small fraction of laboratory-bred adult male zebra finches produce at high frequencies, variant acoustic song profiles consisting of song syllable repetitions, and that the syntactic rule governing these profiles is selectively learned from syllable repeaters by offspring of non-repeaters, during the critical period for song development. Further, subsequent long-term exposure of the tutored repeaters to the songs of non-repeaters cause a decline in the among of repetitions within their song, reflecting a unique form of adult phase song plasticity. The present proposal attempts to extend the above studies, and to initiative an investigation of the neural mechanisms underlying song syllable repetitions and the post- critical period plasticity associated. The specific aims of the proposal are: (1) to study the relative contributions of parental lineage and tutor- pupil interaction in the learned acquisition by juvenile zebra finches of song syllable repetitions; (2) to examine the changes occurring in the songs of adult tutored song syllable repeaters following varying degrees of exposure to a social environment containing only non-repeaters; and (3) to investigate whether differences and changes in the abundance of song syllable repetitions within zebra finch song are associated with alterations in the ability of the neural song control circuit to generate oscillations of neuronal network activity. The experimental approach for the first two specific aims will involve selective breeding, cross-fostering and tutoring of zebra finches, and audio recording and acoustic analysis of their songs. For the third specific aim, it will involve in vitro (brain slice) electrophysiological recordings from song control nuclei of tutored repeaters and non-repeaters at various stages of learning and relearning. This proposal will enable us to initiate a long-term research program that is focused on developing and investigating songbird models of vocal disturbances, and on examining neural plasticity underlying recovery from these disturbances. These basic insights might contribute to the formulation of new hypotheses related to the understanding of the neural basis of human dysfluencies and their treatment.